CN101848480B - Signal-to-interference ratio decision method in actual ICI (Inter-Carrier Interference) elimination of high-mobility OFDM (Orthogonal Frequency Division Multiplexing) cooperative system - Google Patents

Abstract

The invention discloses a signal-to-interference ratio decision method in actual ICI (Inter-Carrier Interference) elimination of a high-mobility OFDM (Orthogonal Frequency Division Multiplexing) cooperative system, which comprises the following steps of: (1) establishing a signal-to-interference ratio model of the capacity of the cooperative system, and analyzing the influence degree of the signal-to-interference ratio on the capacity of the system; (2) determining a value get method of the signal-to-interference ratio of the cooperative method according to a direct channel and the channel characteristics of the cooperative system; (3) calculating a signal-to-interference ratio range which can satisfy system performance requirements according to the signal-to-interference ratio model of the capacity of the cooperative system and the value get method of the signal-to-interference ratio; and (4) determining the elimination process of an elimination algorithm and evaluating the algorithm performance of the elimination algorithm according to the threshold of the signal-to-interference ratio. The method effectively solves the problem of the evaluation on elimination effect during the actual ICI elimination process by using the scheme of evaluating system performance by the signal-to-interference ratio, and the method greatly reduces calculation on the premise of having the same effect with a bit error index measurement elimination algorithm.

Description

Signal interference ratio determination methods in the actual elimination of high-speed mobile OFDM cooperative system ICI

Technical field

The present invention relates to the signal processing method in the radio communication, particularly relate to and disturb the signal interference ratio determination methods of eliminating between a kind of OFDM cooperative system subcarrier.

Background technology

According to the planning of Chinese Railway Long-and Medium-term Development, to the year two thousand twenty, the high speed railway construction mileage of 200 kilometers in China and above speed per hour will above 1.8 ten thousand kilometers, will account for the over half of world's high speed total kilometrage.So the research of the ground ultrahigh speed mobility system of broadband wireless communication take high-speed railway as representative more and more receives people's concern.Because ofdm system has the advantages such as availability of frequency spectrum height, the effective anti-ISI (ISI) of energy, makes the OFDM broadband system can be used as the alternative of high-speed mobile communication system.For ofdm system, become the impact of factor when channel Doppler frequency shift, transmitting-receiving carrier wave frequency deviation (CFO), oscillator phase etc., can cause between subcarrier orthogonality to be destroyed, produce the interference (ICI) between subcarrier, under high-speed mobile environment, Doppler frequency shift is directly proportional with the speed of moving body, becomes the key factor that affects systematic function under the high-speed mobile environment.And bullet train is in order to adapt to the requirement of high-speed cruising, all varying widely aspect sealing and the compartment material, increased the loss of wireless signal, make up Turbo Detection for Cooperative Communication for this reason, reduce car body to the impact of wireless signal loss as far as possible, obtain again simultaneously the collaboration diversity gain, and high-speed railway OFDM in Mobile ICI has following factor to exist when eliminating: (1) Doppler frequency shift constantly changes along with the speed of service of train changes, so ICI also is continuous variation; (2) channel estimating, Doppler estimate it is that error is arranged certainly; (3) removing method of ICI is because the factors such as multipath also are impossible eliminate ICI fully.The ICI elimination algorithm of research is a lot of at present, Kim Byung-Chul, the ICI elimination algorithm that utilizes Doppler's diversity of Lu I-Tai design, the unifrequency backoff algorithm, combined estimation method, the balancing technique algorithm, error performance was improved after these methods were eliminated, but the difficulty in computation of the error rate is large in actual the elimination, and is difficult to know the elimination degree.

Summary of the invention

Problem and shortage in view of above prior art existence, the object of the present invention is to provide the signal interference ratio determination methods in the actual elimination of a kind of high-speed mobile OFDM cooperative system ICI, the method has been simplified calculating greatly under the prerequisite that the effect with error rate index measurement elimination algorithm is equal to, solved the evaluation problem of eradicating efficacy in the actual ICI elimination process.

In order to achieve the above object, the present invention has adopted with following technical proposals:

Signal interference ratio determination methods in the actual elimination of a kind of ICI, its step comprises as follows:

(1) sets up the signal interference ratio model of cooperative system capacity, analyze signal interference ratio to the influence degree of power system capacity;

(2) according to the characteristic of channel of cooperative system direct channels and cooperative system, determine the obtaining value method of cooperative system signal interference ratio;

(3) according to signal interference ratio model and the signal interference ratio obtaining value method of cooperative system capacity, calculate and satisfy the signal interference ratio scope that systematic function requires;

(4) according to the thresholding of signal interference ratio, determine the elimination process of elimination algorithm, and estimate the elimination performance of elimination algorithm.

The signal interference ratio of setting up cooperative system described in the above-mentioned steps (1) is expressed as:

$\mathrm{SIR}=\frac{E\left\{\frac{{\sin }^2\left(\mathrm{\π\ϵ}\right)}{\mathrm{si}{n}^2\left(\frac{\mathrm{\π\ϵ}}{N}\right)}\right\}}{\underset{k=0,k\≠m}{\overset{N-1}{\mathrm{\Σ}}}E\left\{\frac{{\sin }^2\mathrm{\π}(k-m+\mathrm{\ϵ})}{{\sin }^2\mathrm{\π}\left(\frac{k-m+\mathrm{\ϵ}}{N}\right)}\right\}}$

Wherein N is sub-carrier number, and ε is the normalization frequency deviation of relative subcarrier spacing, and k, m are the subcarrier sequence numbers, and k-m refers to the spacing of k bar and m bar subcarrier, and E{} represents the content in the bracket is got mathematic expectaion.

If system bandwidth is B, the capacity when not existing ICI to disturb in the system is

Wherein S is signal power, N ₀Be noise power, and when existing ICI to disturb, signal is write as S=S ₀+ S _ICI, S wherein ₀Be useful signal part, S _ICIBe the ICI interference sections.This moment, the signal interference ratio SIR of system was:

The channel capacity that obtains this moment is:

$C_I=B{\log }_2(1+\frac{S_0}{S_{\mathrm{ICI}}+N_0})$

$={B\log }_2(1+\frac{\frac{\mathrm{SIR}}{\mathrm{SIR}+1}\mathrm{SNR}\&CenterDot;{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HSA00000114822100041.png"\; state="\{\{state\}\}">N</figure-callout>}}_0}{\frac{1}{\mathrm{SIR}+1}\mathrm{SNR}\&CenterDot;{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HSA00000114822100041.png"\; state="\{\{state\}\}">N</figure-callout>}}_0+N_0})$

$=B{\log }_2(1+\mathrm{SNR}-\frac{{\mathrm{<figure-callout\; id="2"\; label="SNR"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">SNR</figure-callout>}}^2+\mathrm{SNR}}{\mathrm{SNR}+\mathrm{SIR}+1})$

Therefore the signal interference ratio model that obtains power system capacity is:

$\frac{{\mathrm{<figure-callout\; id="0"\; label="C\; I\; C"\; filenames="HSA00000114822100041.png"\; state="\{\{state\}\}">C</figure-callout>}}_I}{C_{}}=\frac{{\log }_2(1+\mathrm{SNR}-\frac{{\mathrm{<figure-callout\; id="2"\; label="SNR"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">SNR</figure-callout>}}^2+\mathrm{SNR}}{\mathrm{SNR}+\mathrm{SIR}+1})}{{\log }_2(1+\mathrm{SNR})}$

Here C _I/ C ₀Be the capacity that has the ICI interference and the ratio that does not have the capacity of ICI interference.

Signal interference ratio SINR1 and the SINR2 of direct channels and co-channel were respectively when above-mentioned steps (2) sub-carriers number was larger:

$\mathrm{SINR}1=\frac{\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">N</figure-callout>}}^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)}}{(1-\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">N</figure-callout>}}^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)})+\frac{1}{a_1}\&CenterDot;\frac{1}{{\mathrm{SNR}}_1}}$

$\mathrm{SINR}2=\frac{\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">N</figure-callout>}}^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)}}{(1-\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">N</figure-callout>}}^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)})+\frac{1}{a_2}\&CenterDot;\frac{1}{{\mathrm{SNR}}_2}}$

Wherein SNR1 and SNR2 are respectively the signal to noise ratio of direct channels and co-channel, a ₁And a ₂Be respectively the pad value of direct channels and co-channel.Can find out in identical signal interference ratio situation the Capacity Ratio direct channel of collaborative passage much higher by emulation.Therefore cooperative system signal interference ratio value can be carried out from collaborative passage.

C in the above-mentioned steps (3) _I/ C ₀Increase with signal interference ratio SIR increases, but its rate of change diminishes gradually, and the definition rate of change is Cv, then can be pushed away by the signal interference ratio model:

$\mathrm{Cv}=\frac{{\mathrm{<figure-callout\; id="2"\; label="SNR"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">SNR</figure-callout>}}^2+\mathrm{<figure-callout\; id="2"\; label="SNR\; ln"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">SNR</figure-callout>}}{\ln }\&CenterDot;\frac{1}{(1+\mathrm{SNR}-\frac{{\mathrm{<figure-callout\; id="2"\; label="SNR"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">SNR</figure-callout>}}^2+\mathrm{SNR}}{\mathrm{SNR}+\mathrm{SIR}+1})\&CenterDot;{(\mathrm{SNR}+\mathrm{SIR}+1)}^2}$

To different signal to noise ratios, the variation of Cv all diminishes gradually along with the increase of signal interference ratio, that is to say C _I/ C ₀Increase with signal interference ratio SIR is fewer and feweri, but the transformation rate of the different Cv of signal to noise ratio is different, therefore can determine according to different signal to noise ratios the scope of signal interference ratio.

According to the thresholding of signal interference ratio, determine the elimination process of elimination algorithm in the above-mentioned steps (4), and estimate the elimination performance of elimination algorithm.The signal of cooperative system purpose user and collaborative point can be expressed as:

$Y_{\mathrm{sd}}\left(k\right)=H_{\mathrm{sd}}\left(k\right)V\left(k\right)S\left(0\right)+\underset{l=0,l\&NotEqual;k}{\overset{N-1}{\mathrm{\&Sigma;}}}{H}_{\mathrm{sd}}\left(l\right)V\left(l\right)S(l-k)+n_{\mathrm{sd}}\left(k\right)$

H wherein _Sd(k) be the channel gain of source node S and destination node D, n _SdIt is noise.First of following formula is useful signal, and second is because the distracter of the ICI that Doppler frequency shift produces passes through estimated signal V (k) for following formula, thereby can calculates easily the signal interference ratio of system.Namely just can obtain the transmission performance of its system by the signal interference ratio of judging system.

Signal interference ratio determination methods in the actual elimination of ICI of the present invention has the following advantages compared with prior art: the method is after the relation of research signal interference ratio and Doppler frequency shift, set up the signal interference ratio model of ICI on the channel capacity impact, on this basis, in conjunction with high-speed mobile OFDM synergy system model and channel selection algorithm, signal interference ratio model and signal interference ratio obtaining value method according to the cooperative system capacity, the signal interference ratio scope that systematic function requires is satisfied in calculating, show by emulation, this signal interference ratio determination methods and error rate index are weighed the elimination algorithm effect and are equal to, and in actual elimination process, its easier calculating has solved the evaluation problem of eradicating efficacy in the actual ICI elimination process.

Description of drawings

Fig. 1 is the flow chart of the signal interference ratio evaluation method in the actual elimination of ICI of the present invention;

Fig. 2 is that sub-carrier number is the analogous diagram that 1024 o'clock signal interference ratios change with relative frequency deviation;

Fig. 3 is signal to noise ratio C when being respectively 10dB, 20dB, 30dB _I/ C ₀Analogous diagram with signal interference ratio (dB) relation;

Fig. 4 is the mode figure of cooperative system;

Fig. 5 is the capacity comparison analogous diagram of signal to noise ratio cooperative system direct channel and collaborative passage when being respectively 10dB, 20dB, 50dB, 100dB;

Fig. 6 is signal to noise ratio C when being respectively 10dB, 20dB, 30dB _I/ C ₀Rate of change Cv and the analogous diagram of signal interference ratio (dB) relation;

Fig. 7 is that signal to noise ratio is respectively 10dB, 20dB, 30dB, the analogous diagram of signal interference ratio corresponding Cv when changing from 40dB to 50dB;

Fig. 8 is the analogous diagram of signal to noise ratio relative frequency deviation and bit error rate relation when being respectively 10dB, 20dB, 30dB.

Embodiment

Below in conjunction with accompanying drawing embodiments of the invention are described in further detail.

As shown in Figure 1, the signal interference ratio evaluation method in the actual elimination of ICI, its concrete steps are as follows:

(1) sets up the signal interference ratio model of cooperative system capacity, analyze signal interference ratio to the influence degree of power system capacity: suppose that Y (m), X (m) are output and the input signal of ofdm system, H (m) is channel transfer function, W (m) is additive noise, and then the signal of receiving terminal can be expressed as:

$Y\left(m\right)=H\left(m\right)X\left(m\right)S\left(0\right)+\underset{k=0,k\&NotEqual;m}{\overset{N-1}{\mathrm{\&Sigma;}}}H\left(k\right)X\left(k\right)S(k-m)+W\left(m\right)$

Wherein

$S(k-m)=\frac{\sin \mathrm{\&pi;}(k-m+\mathrm{\&epsiv;})}{N\sin \frac{\mathrm{\&pi;}}{N}(k-m+\mathrm{\&epsiv;})}\exp \left[\mathrm{j\&pi;}(1-\frac{1}{N})(k-m+\mathrm{\&epsiv;})\right]$

$S\left(0\right)=\frac{\sin \mathrm{\&pi;\&epsiv;}}{N\sin \frac{\mathrm{\&pi;\&epsiv;}}{N}}\exp \left[\mathrm{j\&pi;}(1-\frac{1}{N})\mathrm{\&epsiv;}\right]$

First of formula is the useful signal item, and second is the interference signal item, and N is sub-carrier number, and ε is the normalization frequency deviation of relative subcarrier spacing, and k, m are the subcarrier sequence numbers, and k-m refers to the spacing of k bar and m bar subcarrier.Then when sub-carrier number was larger, signal interference ratio SIR can be expressed as:

$\mathrm{SIR}=\frac{E\left\{\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{\mathrm{si}{n}^2\left(\frac{\mathrm{\&pi;\&epsiv;}}{N}\right)}\right\}}{\underset{k=0,k\&NotEqual;m}{\overset{N-1}{\mathrm{\&Sigma;}}}E\left\{\frac{{\sin }^2\mathrm{\&pi;}(k-m+\mathrm{\&epsiv;})}{{\sin }^2\mathrm{\&pi;}\left(\frac{k-m+\mathrm{\&epsiv;}}{N}\right)}\right\}}$

If the OFDM symbol period is with the 4 μ s of 802.11e, the highest running speed of bullet train was with 500km/ hour, carrier frequency is that 2.4GHz is example, its normalization Doppler frequency deviation is about 0.004, thus Fig. 2 emulation ε get 0.001 to 0.01 change curve, as can be seen from the figure, increase along with ε, the signal interference ratio of system descends rapidly, the variation of signal interference ratio reaction Doppler frequency deviation, and corresponding one by one.

Suppose channel capacity:

Do not exist this moment ICI to disturb in the system, signal to noise ratio is

Then when existing ICI to disturb in the system, signal can be write as S=S ₀+ S _ICI, S wherein ₀Be useful signal part, S _ICIBe the ICI interference sections.This moment, the signal interference ratio SIR of system was:

The channel capacity that can obtain this moment is:

$C_I=B{\log }_2(1+\frac{S_0}{S_{\mathrm{ICI}}+N_0})$

$={B\log }_2(1+\frac{\frac{\mathrm{SIR}}{\mathrm{SIR}+1}\mathrm{SNR}\&CenterDot;{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HSA00000114822100041.png"\; state="\{\{state\}\}">N</figure-callout>}}_0}{\frac{1}{\mathrm{SIR}+1}\mathrm{SNR}\&CenterDot;{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HSA00000114822100041.png"\; state="\{\{state\}\}">N</figure-callout>}}_0+N_0})$

$=B{\log }_2(1+\mathrm{SNR}-\frac{{\mathrm{<figure-callout\; id="2"\; label="SNR"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">SNR</figure-callout>}}^2+\mathrm{SNR}}{\mathrm{SNR}+\mathrm{SIR}+1})$

So have the capacity of ICI interference and do not exist the ratio of the capacity of ICI interference to be:

Definition C _I/ C ₀Be the signal interference ratio model of channel capacity, expression ICI is to the influence degree of system, C _I/ C ₀Be 1, the expression on system without impact, C _I/ C ₀C when the more serious Fig. 3 of less impact has simulated signal to noise ratio and is respectively 10dB, 20dB, 30dB _I/ C ₀With the relation of signal interference ratio, as can be seen from Figure 3 SIR is less, C _I/ C ₀Less, under the identical SIR, the larger C of SNR _I/ C ₀Less, it is less to illustrate that interchannel noise disturbs, and the ICI impact is just larger.If ε=0.004 as can be seen from Figure 2 for example, SIR also is about 43dB, according to Fig. 3 when the SNR=30dB, C _I/ C ₀≈ 0.993, and namely channel capacity drops to originally 99.3%, and reflection ICI disturbs the influence degree to broadband system.

(2) according to the characteristic of channel of cooperative system direct channels and cooperative system, determine the cooperative system mode of the obtaining value method of cooperative system signal interference ratio: this paper foundation as shown in Figure 4.User among the figure is the portable terminal in the compartment, and cooperation companions is the collaborative point that arranges.In the transfer of data, collaborative point and terminal are made high-speed mobile like this, and collaborative point and terminal room are without high-speed mobile, and be relatively static.The signal of direct channel can produce large loss when passing the compartment, calculate sub-carrier number when larger signal interference ratio SINR1 and the SINR2 of direct channels and co-channel be respectively:

$\mathrm{SINR}1=\frac{\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">N</figure-callout>}}^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)}}{(1-\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">N</figure-callout>}}^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)})+\frac{1}{a_1}\&CenterDot;\frac{1}{{\mathrm{SNR}}_1}}$

$\mathrm{SINR}2=\frac{\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">N</figure-callout>}}^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)}}{(1-\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">N</figure-callout>}}^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)})+\frac{1}{a_2}\&CenterDot;\frac{1}{{\mathrm{SNR}}_2}}$

A in the formula ₁, a ₂Be the transmission factor of direct channels and co-channel, SNR ₁, SNR ₂Be the signal to noise ratio of direct channels and co-channel, Fig. 5 has simulated under the different signal to noise ratios, the relation of signal interference ratio and channel capacity when adopting collaborative passage and adopting direct channel.As seen from Figure 5 in identical signal interference ratio situation, the Capacity Ratio direct channel of collaborative passage much higher.Therefore cooperative system signal interference ratio value can be carried out from collaborative passage.

(3) according to signal interference ratio model and the signal interference ratio obtaining value method of cooperative system capacity, calculate and satisfy the signal interference ratio scope that systematic function requires: C _I/ C ₀Increase with signal interference ratio SIR increases, but its rate of change diminishes gradually, and the definition rate of change is Cv, then can be pushed away by the signal interference ratio model:

$\mathrm{Cv}=\frac{{\mathrm{<figure-callout\; id="2"\; label="SNR"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">SNR</figure-callout>}}^2+\mathrm{<figure-callout\; id="2"\; label="SNR\; ln"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">SNR</figure-callout>}}{\ln }\&CenterDot;\frac{1}{(1+\mathrm{SNR}-\frac{{\mathrm{<figure-callout\; id="2"\; label="SNR"\; filenames="HSA00000114822100012.png,HSA00000114822100031.png"\; state="\{\{state\}\}">SNR</figure-callout>}}^2+\mathrm{SNR}}{\mathrm{SNR}+\mathrm{SIR}+1})\&CenterDot;{(\mathrm{SNR}+\mathrm{SIR}+1)}^2}$

Fig. 6 has simulated the relation of Cv and signal interference ratio, and as can be seen from the figure, to different signal to noise ratios, the variation of Cv all diminishes gradually along with the increase of signal interference ratio, that is to say C _I/ C ₀Increase with signal interference ratio SIR is fewer and feweri, but the transformation rate of the different Cv of signal to noise ratio is different, therefore can determine according to different signal to noise ratios the scope of signal interference ratio.Its corresponding Cv was 20dB if can find out signal to noise ratio as shown in Figure 7 after signal interference ratio amplified from 40dB to 50dB, signal interference ratio greater than 48dB after, the variation of Cv is very little, namely systematic function changes very little.Therefore we can arrange the signal interference ratio value according to system's specific requirement, as the condition of convergence of elimination algorithm, can estimate the eradicating efficacy of judging elimination algorithm simultaneously.

(4) according to the thresholding of signal interference ratio, determine the elimination process of elimination algorithm, and estimate the elimination performance of elimination algorithm: for system shown in Figure 4, the signal of purpose user and collaborative point can be expressed as:

$Y_{\mathrm{sd}}\left(k\right)=H_{\mathrm{sd}}\left(k\right)V\left(k\right)S\left(0\right)+\underset{l=0,l\&NotEqual;k}{\overset{N-1}{\mathrm{\&Sigma;}}}{H}_{\mathrm{sd}}\left(l\right)V\left(l\right)S(l-k)+n_{\mathrm{sd}}\left(k\right)$

H wherein _Sd(k) be the channel gain of source node S and destination node D, n _SdIt is noise.First of following formula is useful signal, and second is because the distracter of the ICI that Doppler frequency shift produces passes through estimated signal V (k) for following formula, thereby can calculates the signal interference ratio of system.Therefore, this paper has proposed the signal interference ratio determination methods that system ICI eliminates, and namely just can obtain the transmission performance of its system by the signal interference ratio of judging system.Fig. 8 has simulated the relation curve of the error rate and frequency deviation when signal to noise ratio is respectively 10dB, 20dB, 30dB, take signal to noise ratio as 20dB, the error rate is 10 ^-4Be example, the frequency deviation of this moment is about 0.002, is 0.002 o'clock according to Fig. 1 frequency deviation, and its corresponding signal interference ratio is about 48dB, i.e. signal interference ratio determination methods and error rate index measurement elimination algorithm effect is equal to.Therefore we can determine that the value of signal interference ratio judges systematic function according to different channel characteristics.

In sum, signal interference ratio determination methods in the actual elimination of high-speed mobile OFDM cooperative system ICI provided by the invention and error rate index are weighed the elimination algorithm effect and are equal to, and in actual elimination process, its easier calculating has solved the evaluation problem of eradicating efficacy in the actual ICI elimination process.

Claims (1)

1. the signal interference ratio determination methods that a high-speed mobile OFDM cooperative system ICI is actual in eliminating, it is as follows to it is characterized in that operating procedure comprises:

(1) sets up the signal interference ratio model of cooperative system capacity, analyze signal interference ratio to the influence degree of power system capacity;

(2) according to the characteristic of channel of cooperative system direct channels and cooperative system, determine the obtaining value method of cooperative system signal interference ratio;

(3) according to signal interference ratio model and the signal interference ratio obtaining value method of cooperative system capacity, calculate and satisfy the signal interference ratio thresholding that systematic function requires;

(4) according to the thresholding of signal interference ratio, determine the elimination process of elimination algorithm, and estimate the elimination performance of elimination algorithm;

The signal interference ratio model representation of the cooperative system capacity of setting up in the described step (1) is:

Wherein Sub-carrier number,

Be the normalization frequency deviation of relative subcarrier spacing,

,

The subcarrier sequence number, Refer to

Bar and

The spacing of bar subcarrier,

Expression is got mathematic expectaion to the content in the bracket;

If system bandwidth is

, the capacity when not existing ICI to disturb in the system is

, wherein

Be signal power,

Be noise power as, and when existing ICI to disturb, signal is write

, wherein

Be the useful signal part,

Be the ICI interference sections; This moment, the signal interference ratio SIR of system was:

, the channel capacity that obtains this moment is:

Therefore the signal interference ratio model that obtains power system capacity is:

Here

Be the capacity that has the ICI interference and the ratio that does not have the capacity of ICI interference;

The signal interference ratio of direct channels and co-channel when described step (2) sub-carriers number is larger

With

Be respectively:

Wherein

With

Be respectively the signal to noise ratio of direct channels and co-channel,

With

Be respectively the pad value of direct channels and co-channel; Find out in identical signal interference ratio situation the Capacity Ratio direct channels of co-channel much higher by emulation; Therefore cooperative system signal interference ratio value is carried out from co-channel;

In the described step (3) With signal interference ratio

Increase and increase, but its rate of change diminishes gradually, the definition rate of change be

, then pushed away by the signal interference ratio model:

To different signal to noise ratios,

Variation all along with the increase of signal interference ratio diminishes gradually, that is to say

With signal interference ratio

Increase and increase fewer and fewerily, but signal to noise ratio is different Transformation rate different, therefore determine the scope of signal interference ratio according to different signal to noise ratios;

The thresholding according to signal interference ratio in the described step (4) is determined the elimination process of elimination algorithm, and estimates the elimination performance of elimination algorithm; The signal indication of cooperative system purpose user and collaborative point is:

Wherein

The channel gain of source node S and destination node D, It is noise; First of following formula is useful signal, and second is because the distracter of the ICI that Doppler frequency shift produces passes through estimated signal for following formula

Thereby, calculate easily the signal interference ratio of system; Namely just obtain the transmission performance of its system by the signal interference ratio of judging system.

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